A Method for the Evaluation of the Critical Temperature of Brittleness with Regard for the Spread of the Experimental Da
- PDF / 721,526 Bytes
- 14 Pages / 594 x 792 pts Page_size
- 69 Downloads / 178 Views
A METHOD FOR THE EVALUATION OF THE CRITICAL TEMPERATURE OF BRITTLENESS WITH REGARD FOR THE SPREAD OF THE EXPERIMENTAL DATA ON IMPACT TOUGHNESS I. V. Orynyak,1, 2 М. N. Zarazovskii,1 and A. V. Bogdan1
UDC 539.3(4)
We propose an original physically justified method for the evaluation of the spread of values of the critical temperature of brittleness. Its principal distinction from the standard method and advantage over this method is that the spread of data is determined according to the source data used for the evaluation of the critical temperature of brittleness but not according to the set of values of this temperature. We introduce quantitative characteristics of a series of impact-toughness tests aimed at finding the critical temperature of brittleness: the effective number of experimental points and the weight (degree of influence) of each of these points on the critical temperature of brittleness. A criterion of sufficiency of the number of values of impact toughness for the adequate determination of the critical temperature of brittleness according to these values is also proposed. We describe numerous experiments that reveal good correlation between the spread of values of the critical temperature of brittleness obtained by the proposed method and the corresponding standard deviations. Keywords: static crack resistance, critical temperature of brittleness, fracture energy of Charpy specimens, reactor vessel, reference specimens.
Guaranteeing the integrity of structural elements of critical industrial objects for the entire service life (including the over-design period) is one of the main problems of the contemporary applied sciences. For thickwall structures, the key condition is to guarantee the required resistance to sudden (brittle) fracture. In this connection, the condition of sufficiently high brittle strength (BS) of a structural element with an expected (or already existing) defect takes the form
KI ≤
K IC , kS
(1)
where K I is the designed stress intensity factor (SIF), K IC is the static crack resistance, and kS is the safe-
ty margin. The static crack resistance of the metal in the intact state strongly depends on the working temperature and is specified, in the normative documents of the nuclear power-generating industry, by the exponential function
K IC (T ) = A1 + A2 eα(T −TK ) ,
(2)
where A1 is the minimum value of the static crack resistance, A2 and α are empirical coefficients, and TK is 1 2
Pisarenko Institute for Problems of Strength, Ukrainian National Academy of Sciences, Kiev, Ukraine. Corresponding author; e-mail: [email protected].
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 51, No. 1, pp. 26–36, January–February, 2015. Original article submitted March 18, 2014. 1068-820X/15/5101–0023
© 2015
Springer Science+Business Media New York
23
24
I. V. ORYNYAK, М. N. ZARAZOVSKII,
AND
A. V. BOGDAN
the critical temperature of brittleness (CTB) of the metal. The curve plotted according to Eq. (2) is indexed by the values of CTB in the countries using wat
Data Loading...
